[GitHub] [tvm] kparzysz-quic commented on a change in pull request #8213: [LLVM] Fix CodeGenLLVM::LinkParameters

[GitBox]

kparzysz-quic commented on a change in pull request #8213:
URL: https://github.com/apache/tvm/pull/8213#discussion_r649302309



##########
File path: src/target/llvm/codegen_llvm.cc
##########
@@ -215,41 +205,29 @@ void CodeGenLLVM::LinkParameters(const Map<String, 
LinkedParam> params) {
 
   llvm::BasicBlock* entry = llvm::BasicBlock::Create(*ctx_, "entry", function);
   builder_->SetInsertPoint(entry);
-  std::vector<llvm::Value*> zero_index_list{llvm::ConstantInt::get(t_int32_, 
0)};
-  std::vector<llvm::Value*> 
zero_array_index_list{llvm::ConstantInt::get(t_int32_, 0),
-                                                  
llvm::ConstantInt::get(t_int32_, 0)};
-  auto args_array = builder_->CreateBitCast(
-#if TVM_LLVM_VERSION >= 50
-      &function->arg_begin()[0],
+
+  auto getArg = [function](int i) -> llvm::Argument* {
+#if TVM_LLVM_VERSION >= 100
+    return function->getArg(i);
+#elif TVM_LLVM_VERSION >= 50
+    return &function->arg_begin()[i];
 #else
-      &(*(function->arg_begin())),
+    return &*std::next(function->arg_begin(), i);
 #endif
-      llvm::ArrayType::get(t_void_->getPointerTo(GetGlobalAddressSpace()), 1));
-  llvm::Value* sid = builder_->CreateBitCast(
-      builder_->CreateLoad(t_void_->getPointerTo(GetGlobalAddressSpace()),
-                           builder_->CreateInBoundsGEP(args_array, 
zero_index_list)),
-      t_int64_);
+  };
+
+  llvm::Type* t_int64_p = t_int64_->getPointerTo(GetGlobalAddressSpace());
+  llvm::Value* sid = builder_->CreateLoad(t_int64_, 
builder_->CreateBitCast(getArg(0), t_int64_p));
+
+  auto ret_tcode = builder_->CreateBitCast(getArg(4), t_int_p);
+  auto ret_value =
+      builder_->CreateBitCast(getArg(3), 
t_void_p_->getPointerTo(GetGlobalAddressSpace()));
 
   llvm::BasicBlock* default_block = llvm::BasicBlock::Create(*ctx_, 
"default_block", function);
-  auto ret_types_array = builder_->CreateBitCast(
-#if TVM_LLVM_VERSION >= 50
-      &function->arg_begin()[4],
-#else
-      &(*(std::next(function->arg_begin(), 4))),
-#endif
-      llvm::ArrayType::get(t_int_, 1)->getPointerTo());
-  auto retval_array = builder_->CreateBitCast(
-#if TVM_LLVM_VERSION >= 50
-      &function->arg_begin()[3],
-#else
-      &(*std::next(function->arg_begin(), 3)),
-#endif
-      llvm::ArrayType::get(t_void_->getPointerTo(GetGlobalAddressSpace()), 
1)->getPointerTo());
   llvm::SwitchInst* switch_inst = builder_->CreateSwitch(sid, default_block, 
params.size() + 1);
 
   builder_->SetInsertPoint(default_block);
-  builder_->CreateStore(llvm::ConstantInt::get(t_int_, kTVMNullptr),
-                        builder_->CreateInBoundsGEP(ret_types_array, 
zero_array_index_list));
+  builder_->CreateStore(llvm::ConstantInt::get(t_int_, kTVMNullptr), 
ret_tcode);

Review comment:
       In fact, in this code
   ```
   define i32 @fred(i32* %a0) {
     %v0 = bitcast i32* %a0 to [1 x i32]*
     %v1 = getelementptr [1 x i32], [1 x i32]* %v0, i32 0, i32 0
     %v2 = load i32, i32* %v1, align 4
     ret i32 %v2
   }
   ```
   the use of the array type gets optimized out (in `instcombine`):
   ```
   $ opt -S -instcombine < 1xi32.ll
   ; ModuleID = '<stdin>'
   source_filename = "<stdin>"
   
   define i32 @fred(i32* %a0) {
     %v2 = load i32, i32* %a0, align 4
     ret i32 %v2
   }
   ```




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